Question

A sample of phosphorus has 0.5 moles of P4 molecules, what is the mass of the sample?

Answer 1

First, the molar weight of the molecular phosphorus P₄ is:

$$M(P_{4})=4*31g/mol=124g/mol$$

And now, we can calculate the mass of the phosphorus P₄:

$$m(P_{4})=n(P_{4})*M(P_{4})=0.5mol*124g/mol=62g$$

Thus, the mass of 0.5 mol of P₄ molecules is 62 grams.